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Discussion Starter · #1 · (Edited)
Two competing issues regarding my 12 mpg. #1, I think it's my brake system, spefically either the brake lines are gunked or maybe the master cylinder is bad. Found right front caliper draging, so under a time pinch I replaced it with a refurbished. This helped, but only temporarily and so I'm back down to 12 mpg.

But my truck is also running rich, as evidenced by the carbon builld up on the tailpipe.

I've checked the TPS, replaced the plugs, plug wires, cap and rotor, and I've timed it.

I can't pull ecu codes easily because the CEL is burnt out. Over the summer I tapped into the ECU with a bulb tester and was getting the knock sensor, but on visual inspection it looks okay. I may just replace the wire, though that doesn't look as easy as it sounds.

So, I took a look at my throttle body and MAF. More on the MAF in a moment.

The throttle body looked clean, but just inside, not so much:

Clean Throttle body

Not so clean just inside

And here you can see the very back of the plenum, the part in focus, where it's pretty nasty. Do you think I should assume the injectors need cleaning?

As for the MAF, well, I really wish that I had read all up and down about not taking out those two little screws; I think I diverted disaster because I didn't pull too hard and so as soon as there was resistance on the MAF connector, I stopped and put it back together.

AFter I put it together, I checked the Ohm resistance and all were in specs, I think. I've put them below.

Link to specs page for MAF (or VAF)

To see my measurements, I've created a table but can't format it here very well, so click this link to see it.

UPDATE: I also did
4crawler's dynamic test, and the maf seems to be working fine

I've got a digital ohm meter, and so, when I test the two test probes together, I basically get zero, which I take to mean that there is zero resistance. As for getting infinity, I get a vertical line on the left side of the display. Am I'm reading that right, that the vertical line means 'infinity?' If so, woo-hoo! MAF is in specs.

Of course, that means I need to figure out, still, why I'm running rich.

I took a look at the knock sensor, just to see if was loose, or if the wires looked bad. They looked okay, but I'll revisit that later.

for now, I think it's my brake lines causing most of my poor gas mileage
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